The present invention relates to a binocular with an interpupillary adjustment mechanism.
FIGS. 1 and 2 are a perspective view and an exploded perspective view of a conventional binocular having an interpupillary adjustment mechanism. As shown in FIG. 1, in such conventional binocular 100, eyepiece optical axes of left and right eyepiece portions 103 and 104 are respectively off-centered with object optical axes XL and XR of front-most lenses 101 and 102 of left and right object systems. The eyepiece portions 103 and 104 are swingable about the object optical axes XL and XR respectively, so as to vary the distance between left and right eyepiece portions 103 and 104.
As shown in FIG. 2, the binocular 100 includes left and right rotatable bodies 105 and 106 respectively accommodating left and right telescope systems. The left rotatable body 105 includes a front barrel 105a and a rear barrel 105c which are parallel but off-centered with each other and an intermediate barrel 105b provided between two barrels 105a and 105c. Similarly, the right rotatable body 106 including a front barrel 106a and a rear barrel 106c and an intermediate barrel 106b. The binocular 100 further includes a support arrangement (a front support 110 and a rear support 111) which supports the rotatable bodies 105 and 106 so that the rotatable bodies 105 and 106 can be rotated about the object optical axes XL and XR, thereby to swing the rear barrels 105c and 106c and to vary the distance between the eyepiece portions 103 and 104.
In order to synchronize the rotation of the left and right rotatable bodies 105 and 106, a pair of sector gears 107 and 108 are provided on facing curved walls of the intermediate barrels 105b and 106b. The sector gears 107 and 108 engage with each other. When an observer rotates one of the rotatable bodies 105 and 106, the other is also rotated due to the engagement of the sector gears 107 and 108. Thus, the interpupillary adjustment is symmetrical.
FIGS. 3A and 3B are rear views of the rotatable bodies, respectively showing the state the interpupillary distance is maximum and the state the interpupillary distance is minimum. As shown in FIGS. 3A and 3B, there is a space 120 between two facing curved walls of the intermediate barrels 105b and 106b. In order to minimize the binocular 100, it is preferable to utilize the space 120 for accommodating an operation knob (for example, a focus adjusting knob). However, since the sector gears 107 and 108 move into the space 120 as shown in FIG. 3B, it is difficult to utilize the space 120 for accommodating the operation knob.